FIELD OF THE INVENTION
The invention relates to a power semiconductor component.
Such components are needed particularly in the development of inexpensive, reliable configurations for driving DC motors constructed for currents of 10 to approximately 50 A. The employment of such components is useful primary in the automotive field, for instance in window raisers, seat adjusters, windshield washers, sliding roofs, and so forth. In order to provide for the DC motors to be triggered, a so-called H bridge configuration is needed. That is a full bridge with four switches, two each connected in series between a feed voltage and ground. The DC motor is connected between connecting points of the switches. Therefore, the feed voltage can be connected bidirectionally to the motor. A single branch of the configuration is also referred to as a half-bridge. The residual resistance of the switches causes power loss and thus impairs the efficiency of the system.
In the case of relatively low motor currents, the bridge configuration can be integrated monolithically. So-called hybrid technologies which are preferably used for that purpose make it possible for analog and digital supplementary functions to be integrated monolithically along with D-MOS power switching transistors. Due to the relatively high on-state resistance R.sub.DSON, the load current, at acceptable power losses for those structures, remains below about 10 A. The reason for the relatively high on-state resistances can be found in the lateral current flow and in the fact that there are two relatively high impedance bonded connections. One such component is described in a catalog of the firm Siliconix, entitled: Power Products Data Book 1994, p. 1-93.
Electromechanical relays are therefore used more and more today at higher current values. However, those components have disadvantages, such as poor reliability and a limited service life. They are hard to process, and they are neither resistant to vibration nor low in noise. All of those disadvantages can be avoided with currently available so-called vertical technologies, in which only a single bonded connection is needed. In that technology, a semiconductor chip is mounted on a cooling surface that acts at the same time as a drain terminal and therefore saves one high-impedance bonded connection. With such a technology, the turn-on resistances are therefore at extremely low values.
If one wishes to construct a bridge drive with those components, then a plurality of cooling surfaces are needed, which have to be galvanically separated. A bridge or even a half bridge can certainly not be integrated monolithically. Only the two high-side switches can be made on a chip, since the rear sides of the chip are the respective drain terminals. Thus for an aforementioned H bridge configuration, three chips are needed, which are mounted on three separate cooling surfaces. They are accommodated in a package with relatively high heat resistance, for instance. The bridge circuit can therefore be used only for high pulsating currents or low continuous currents. Packages with low heat resistances are very expensive and therefore do not prevail. Mounting on ceramic or other substrates is conceivable but at present is also too expensive. The least expensive version is to interconnect discrete elements, that is one double high-side switch and two low-side switches.